I represent a DisplayScreen that is not part of the Squeak universe. Subclasses must implement the appropriate primitives for creating, destroying and allocating the appropriate external objects.

Note: It is assumed that all external display surfaces are accessible by FXBlt, meaning that any support code must register the surfaces with the surface plugin. This requires that the support code will have a way of accessing the bits of the surface. Although this can be terribly expensive (such as on X where a roundtrip to the server might be required or for an OpenGL display where glReadPixels usually is slow as hell) the appropriate methods should be implemented. This allows for a gradual transition to less expensive model (such as implementing an X11Canvas supporting the drawing primitives of X) and is therefore the preferred solution.

In the eventual case that it's known that BitBlt/FXBlt will *never* be used in conjunction with a particular drawing surface, the support code should return a handle that is a) not a SmallInteger (these are used by the surface plugin) and b) not of the 'bitsSize' of a Form. One possible representation for such a handle would be a ByteArray of a non-integral word size (e.g., a ByteArray of size 5,6, or 7). In this case, all attempts to use FXBlt with the drawing surface will simply fail.

	blitting support
	copyBits:from:at:clippingBox:rule:fillColor:map: displayOn:at:clippingBox:rule:fillColor: fill:rule:fillColor: isBltAccelerated:for: isFillAccelerated:for:

	form support
	allocateForm: destroyForm: rgbaBitMasksOfForm:

	initialize-release
	destroy finish flush release shutDown

	primitives-display
	primBltFast:from:at:from:extent: primBltFast:to:at:from:extent: primCreateDisplaySurface:width:height: primDestroyDisplaySurface: primDisplay:colorMasksInto: primFill:color:x:y:w:h: primFinish: primFlush: supportsDisplayDepth:

	primitives-forms
	primAllocateForm:width:height: primDestroyForm: primForm:colorMasksInto:

	primitives-textures

	private
	setExtent:depth:

	testing
	hasNonStandardPalette isExternalForm

	texture support

	accessing	top
	colormapFromARGB Return a ColorMap mapping from canonical ARGB pixel values into the receiver
	defaultBitBltClass Return the BitBlt version to use when I am active
	defaultWarpBltClass Return the WarpBlt version to use when I am active
	rgbaBitMasks Return the masks for specifying the R,G,B, and A components in the receiver

	blitting support	top
	copyBits:from:at:clippingBox:rule:fillColor:map: Attempt to accelerate blts to the receiver
	displayOn:at:clippingBox:rule:fillColor: Attempt to accelerate blts to aDisplayMedium
	fill:rule:fillColor: Replace a rectangular area of the receiver with the pattern described by aForm according to the rule anInteger.
	isBltAccelerated:for: Return true if the receiver can perform accelerated blt operations by itself. It is assumed that blts of forms allocated on the receiverusing Form>>over may be accelerated. Although some hardware may allow source-key blts (that is, Form>>paint or similar) this is usually questionable and the additional effort for allocating and maintaining the OS form doesn't quite seem worth the effort.
	isFillAccelerated:for: Return true if the receiver can perform accelerated fill operations by itself. It is assumed that the hardware can accelerate plain color fill operations.

	form support	top
	allocateForm: Allocate a new form which is similar to the receiver and can be used for accelerated blts
	destroyForm: Destroy the given external form
	rgbaBitMasksOfForm:

	initialize-release	top
	destroy Destroy the receiver
	finish Flush the receiver
	flush Flush the receiver
	release I am no longer Display. Release any resources if necessary
	shutDown Minimize Display memory saved in image

	primitives-display	top
	primBltFast:from:at:from:extent: Primitive. Perform a fast blt operation. Return the receiver if successful.
	primBltFast:to:at:from:extent: Primitive. Perform a fast blt operation. Return the receiver if successful.
	primCreateDisplaySurface:width:height: Primitive. Create a new external display surface. Return the handle used to identify the receiver. Fail if the surface cannot be created.
	primDestroyDisplaySurface: Primitive. Destroy the display surface associated with the given handle.
	primDisplay:colorMasksInto: Primitive. Store the bit masks for each color into the given array.
	primFill:color:x:y:w:h: Primitive. Perform an accelerated fill operation on the receiver.
	primFinish: Primitive. Finish all rendering operations on the receiver. Do not return before all rendering operations have taken effect.
	primFlush: Primitive. If any rendering operations are pending, force them to be executed. Do not wait until they have taken effect.
	supportsDisplayDepth: Return true if this pixel depth is supported on the current host platform.

	primitives-forms	top
	primAllocateForm:width:height: Primitive. Allocate a form with the given parameters
	primDestroyForm: Primitive. Destroy the form associated with the given handle.
	primForm:colorMasksInto: Primitive. Store the bit masks for each color into the given array.

primitives-textures

top

	private	top
	setExtent:depth: Create a 3D accelerated display screen

	testing	top
	hasNonStandardPalette Quite possible.
	isExternalForm Sorta. Kinda.

texture support

top